Growth responses of coliform bacteria to antibodies directed against ferric enterobactin receptor FepA

he role of ferric enterobactin receptor FepA in the pathogenesis of bovine mastitis caused by coliform bacteria was investigated. All isolates of E. coli (n = 25), and K. pneumoniae (n = 25) were positive for siderophore production. Immunoblot technique in conjunction with rabbit anti-FepA serum showed that all isolates expressed 81-kDa FepA under iron-restricted condition. FepA is widely distributed and conserved among coliform isolates from naturally occurring bovine IMI.;The serum and milk IgG responses of lactating dairy cows were determined following immunization with purified FepA. Serum and whey IgG titers to FepA from cows vaccinated with either 100 or 500 ;The abilities of purified bovine anti-FepA IgG and a murine monoclonal antibody directed against FepA to inhibit the growth of coliform bacteria were determined in vitro. Growth of all E. coli isolates was significantly inhibited by the addition of monoclonal antibody to synthetic medium containing apolactoferrin. Antigenic variation in the enterobactin binding site resulted in a low percentage of K. pneumoniae isolates that were inhibited by the monoclonal antibody. Addition of 4 mg/ml of purified bovine IgG directed against FepA to synthetic medium resulted in significant growth inhibition for both E. coli and K. pneumoniae isolates. In dry cow secretion, growth of E. coli isolates was inhibited by addition of 4 mg/ml of bovine anti-FepA IgG. Less than half of K. pneumoniae isolates (43%) were inhibited by IgG from FepA immunized cows. Supplementing 50...